Dyes and lakes are used to provide attractive colors to foods, cosmetics and pharmaceuticals. Lakes are insoluble coloring matters. They can be dispersed in a solution to provide color and opalescence. Most lakes are made from a dye immobilized onto the surface of an aluminum substratum to form an insoluble complex (see for example U.S. Pat. Nos. 833,602, 2,053,208 and 3,909,284 which describe methods of producing artificial lakes).
Lakes are opaque and their color is seen by reflectance of light. They are used essentially anywhere insoluble pigments are appropriate, including in dry or oil-based products where there is insufficient moisture for water-soluble dyes, or products where migration of a soluble dye would be a problem. Typical applications include, but is not limited to, colored candy coating of panned candies, breakfast cereals, nuts, multilayered food stuff (e.g., cakes) cosmetics (e.g., blush and lipsticks) and pharmaceutical capsules, dragees, tablets and the like. Most lakes are made of chemically-synthesized artificial dyes. An exception to this is carmine, an aluminum lake of natural carminic acid extracted from the insect Dactilopius coccus. 
Various means of producing water insoluble coloured material have been developed. One approach has been to immobilize dyes onto the surface of insoluble compounds. U.S. Pat. No. 4,475,919 describes a method to lake natural dyes onto the surface of natural insoluble polymers such as cellulose, microcrystalline cellulose, cellulose derivatives such as ethyl cellulose, starch or starch derivatives. Examples of natural dyes include anthocyanins, turmeric and annatto. An aluminum salt is used as a dyeing aid. In addition, JP Patent No. 10330637 teaches a method to immobilize natural lake dyes onto the surface of an aluminum substratum namely aluminum hydroxide. In both instances, the natural dyes are adsorbed onto a surface and are therefore not protected from detrimental physical or chemical factors. Furthermore, the use of aluminum as a substratum is of growing concern since it has been recognized for some time as a neurotoxic agent (Lukiw W J (1997) Alzheimer's Disease and Aluminum. In “Minerals and metal neurotoxicology” CRC Press, Boca Raton, Fla., pp. 113-125).
Yet another approach for producing water insoluble coloured material has been to develop a media for the dispersion of water insoluble dyes and lakes. U.S. Pat. No. 5,393,333 teaches a method of dispersing lakes in a mixture comprised of a film forming substance, a colouring and a plasticizer. The mixture is taught as useful in coloring the surface of medicinal tablets. PCT application No. 00150714US describes a method to disperse artificial lakes by use of a mixture of a hydrocolloid, namely gelatine and of a fatty acid. The fatty acid serves in maintaining viscosity of gelatine and in facilitating the dispersion of lakes.
Dispersion media have also been developed for natural water-insoluble dyes. European patent application No. 01219292/EP-A1 reports the use of a soy protein isolate to disperse carotenoids namely astaxanthin, canthaxanthin, lutein, zeaxanthin, citraxanthin and, β-apo-8′-caroteneethylester in an aqueous solution. The soy protein isolate was partially hydrolysed using enzymes to improve hydrocolloid properties. It has been demonstrated that carotenoids dispersed in such hydrocolloid are protected against oxidation by free radicals and retain their antioxidant activity. Similarly, International publication WO 03045167 describes methods to stabilize crystalline lycopene by reacting lycopene with a native soy protein isolate or an alkali-treated soy protein isolate. U.S. Pat. No. 6,719,839 describes a method to obtain a dispersed suspension of a natural dye in a hydrocolloid solution. Most examples of hydrocolloids are mixtures of gelatine and Arabic gum. The solubilisation of the mixture of dye and hydrocolloid is carried out at alkaline pH. Natural water-insoluble dyes include porphyrin, turmeric, vegetable black and annatto. The method can also be used with the natural lake, carmine.
Many of the above-mentioned water-insoluble dyes are known to bind to proteins. Thus aqueous solutions of water-soluble proteins can be used to maintain homogenized mixtures of protein and water-insoluble dyes dispersed. It can be expected that the shelf life of such preparations could be extended by the use of antimicrobial compounds. They might nevertheless have a limited shelf life due to the high water activity of the solutions and could not be used to colour oil-based products unless they were dried. Furthermore, because of limitations on the concentration of the protein in the aqueous solutions, it can be expected that a bulking agent such as maltodextrin would have to be added to the dispersed colour solution to carry out spray drying. The presence of maltodextrin in the spray-dried colour could provoke a fading of the colour when used in lipid-based products wherein maltodextrin would not dissolve.
Several other patents describe methods of rendering dyes insoluble by encapsulation into an insoluble matrix. U.S. Pat. No. 6,037,000 describes a method of producing small insoluble particles of encapsulated dye or lake. It involves dispersing the lake or dye into a melted matrix and forming small solid particles of the mixture by spray congealing. The only examples given are for the encapsulation of artificial lakes in a matrix comprised of polyethylene. As such, applications seem limited to toiletries and cosmetics because polyethylene is not suitable for foods. In addition, European Patent EP 0 750 854 describes a method to encapsulate dyes in an insoluble protein matrix. The method involves mixing the dye and a protein in water, adding a non-polar phase and homogenizing to obtain a water-in-oil dispersion and subjecting same to very high pressures between 15,000 and 200,000 psig to render the protein matrix insoluble. The coloured particles can then be separated from the non-polar phase and dried. This process involves the use of expensive pressurized equipments and can only be carried out batch-wise.
U.S. Pat. No. 4,230,687 describes a method to encapsulate flavourings into a melt of encapsulating mixture comprised of 44% caseinate based on the weight of the encapsulate and of the encapsulating mixture. The resulting product which is described as sticky, viscous, plastic and non-flowable, is shaped into a sheet, dried and ground into a powder. As with other processes described above, solubilisation of the protein requires the use of an alkali that can be detrimental to alkali-sensitive active agents such as natural dyes of the group of anthocyanins. Furthermore, heating of the protein matrix generates Maillard reactions causing the formation of brown pigments that would alter the colour of an encapsulated dye.
Encapsulation of active agents can also be accomplished by extrusion. Extrusion is a continuous process that carries out several functions namely mixing and kneading liquid and solid ingredients, cooking them under a pressure that results in the formation of a melt and shaping ingredient by use of a dye. This process is accomplished over a relatively short period, typically between 1 to 2 minutes and heat may be applied over a much shorter period. Many extruded food products such as pasta, pet food, breakfast cereals and meat extenders have been coloured with artificial dyes. In most instances, extruded products are comprised of a substantial proportion of carbohydrates, e.g., starch of extruded flours, meals or grits, or syrup in extruded confectioneries, that limits the impermeability of extruded products to water. For example, Kinnison (1971; Effects of extrusion on food colors; Snack Food Color Service Lab., Warner-Jenkinson Co. 60(10): 50-51) reports the extrusion of corn grits and eight artificial dyes at temperatures that provoke product expansion. It was reported that the artificial dyes could sustain the high temperatures used in this type of process. U.S. Pat. No. 6,436,455 describes a process to manufacture marshmallows by extrusion of a mixture of gelatine, syrup and dye. It is likely that natural dyes would be destroyed in such high temperature processes. Furthermore, the high carbohydrate content and porous nature of the expanded products are expected to convey little protection against moisture.
There have been a few reports on the use of natural dyes in extruded products. Maga and Kim (1990; Stability of natural colorants [annatto, beet, paprika, turmeric] during extrusion cooking. Lebensmittel-Wissenchaft & Technologie, 23(5): 427-432) have studied the stability of natural dyes namely annatto (bixin and norbixin), beet red, paprika oleoresin and turmeric, in rice flour extruded at 125° and 155° C. The dyes were shown to be sensitive to heat, the most sensitive being beet red. Berset (1989; Color; Chapter 12. In: “Extrusion cooking”. Mercier C et al., Eds, AACC, St. Paul, Minn., pp. 371-385) has performed a similar study on β-carotene, canthaxanthin and annatto incorporated by extrusion in rice starch. Results also showed a sensitivity of the colourings to heat.
Extrusion can be carried out at temperatures low enough to enable the encapsulation of flavor compounds using a non-conventional extrusion setup. U.S. Pat. No. 5,756,136 describes a method to encapsulate cinnamaldehyde into a mixture of carbohydrates and whey using an extruder. Cinnamaldehyde which is the major component of cinnamon flavor, inhibits the leavening of dough by yeasts. It was demonstrated that the encapsulated cinnamaldehyde could be incorporated into dough without inhibiting yeast leavening. U.S. Pat. No. 6,790,453 describes the composition of a matrix used to encapsulate medications, pesticides, vitamins, preservatives and flavoring agents. The matrix comprises various mixtures of Arabic gum, polyols and gelatine. Matrices used in the encapsulation of flavor compounds possess polar characteristics that enable the release of flavor compounds so that they can be smelled and tasted in aqueous media.
There is growing concern over the safety of artificial dyes that are used in lakes. In fact, in recent years, the only colourings that have been withdrawn from the marketplace because of evidence of toxicity have been artificial. Furthermore, there is also concern about the use of aluminum since it has been recognized for some time as a neurotoxic agent and controversial etiopathogenic factor in several neurological disorders (Lukiw W J; 1997; Alzheimer's Disease and Aluminum. In “Minerals and metal neurotoxicology” CRC Press, Boca Raton, Fla., pp. 113-125). In addition, although Carmine (i.e., carminic acid extracted from an insect plated into an aluminum salt) is generally used as a natural lake, its animal origin is not deemed suitable for kosher, Hallal and vegetarian diets.
Thus, there remains a need for natural non-toxic colouring agents.
More particularly, there remains a need for natural lakes free of aluminum or other neurotoxic agents or suspected health hazardous agents for colouring foods, cosmetics, medicines and the like.
There also remains a need for bright, long lasting, unfading natural lake dyes.
Furthermore, there remains a need for an improved and inexpensive process to produce natural lake dyes which does not use natural dye damaging agents (e.g., alkali solutions) or extensive heating thereby causing a Maillard Reaction and altering the color of the natural dye.
In addition, there remains a need for an improved process which enables the encapsulation of labile active agents, such as natural dyes, which limits the release of the active agent in water.
There remains a need for natural lakes suitable for particular diets such as vegetarian, kosher and Hallal diets. The present invention seeks to meet these needs and other needs.
The present description refers to a number of documents, the content of which is herein incorporated by reference in their entirety.